The clouding behavior of surfactants in water with increasing temperature has several practical applications. For example, the defoaming action of surfactants becomes effective just above their cloud point. See Otten et al, “Anionic Hydrotropes for Industrial and Institutional Rinse Aids”, JAOCS; 63(8); 1078; 1986 (the entire content of which is incorporated expressly hereinto by reference). An end user will therefore select a particular surfactant for specific problem solving abilities such as wetting, detergency, foaming, defoaming and the like. In cleaning applications such as machine dish washing, the properties noted above are important. Since the water temperature in dish washing applications is relatively high, the surfactant selected often cannot meet all of the desired performance criteria. As a result, additives are typically included with the surfactant to achieve the desired solubilization. However, often times, when all other properties of the surfactant are in agreement for a specific application, often the surfactant's cloud point is too low. While the cloud point can be engineered by altering the surfactant's chemical structure, such structural alteration usually is accompanied by a change in one of its other properties thereby making it no longer useful for the intended application.
Recently, it has been suggested that certain electrolytes may be added so as to adjust the cloud point of a block copolymer surfactant comprised of an ethylene oxide (EO) and propylene oxide (PO) units. Pandya et al, “Effect of Additives on the Clouding Behavior of an Ethylene Oxide-Propylene Oxide Block copolymer in Aqueous Solution”; J.M.S-Pure Appl. Chem; A30(1); 1; 1993 (the entire content of which is expressly incorporated hereinto by reference). However, the technique described in this paper involves the addition of foreign materials often adding extra cost and unwanted interferences in the surfactant's performance.
Polyether polyol surfactants are typically prepared by the reaction of monomeric or polymeric initiators containing one or more active hydrogen-containing group(s), such as OH, NH2, NH, CO2H and the like, with alkylene oxides. The alkylene oxide reactions with the active hydrogen-containing compounds are catalyzed with alkaline catalysts such as potassium hydroxide and sodium hydroxide. At the end of the reaction, the catalyst is deactivated by either removing the catalyst physically from the resulting reactant mixture or by adding an acid, such as acetic acid, phosphoric acid, sulfuric acid and the like, in order to neutralize the catalyst. The most cost-effective way of deactivating the alkaline catalyst is by neutralizing the catalyst with an acid and leaving the resulting salt physically in the polyether polyol reaction product.
It has now been surprisingly discovered that, by neutralizing a surfactant which is the alkaline-catalyzed reaction product between a monomeric or polymeric compound (initiator) having at least one active hydrogen group and an alkylene oxide with a fatty acid, the cloud point of the surfactant may be raised as compared to otherwise identical surfactants which have not been neutralized (i.e., non-neutralized surfactants) and/or otherwise identical surfactants that have been neutralized with conventional non-fatty acids, such as acetic acid, phosphoric acid, sulfuric acid and the like.
These and other aspects and advantages will become more apparent after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof.